1. Field of the Invention
The present invention relates to a wrist exerciser that is in the form of a hollow sphere inside which a rotor is rotatably support so that by manually rotating the hollow sphere, the rotor is rotated inside the hollow sphere to thereby effect exercising of hand and wrist related muscles, and in particular to a wrist exerciser that is configured to auto-start the rotor by generating an initial auxiliary starting force acting on the rotor to facilitate regular operation of the wrist exerciser.
2. The Related Arts
A wrist exerciser is helpful in exercising hand and wrist related muscles, and is of particular therapeutic effect for rehabilitation. Examples are disclosed in Taiwan Patent No. 135058 and U.S. Pat. No. 5,800,311. Such devices are suitable for operating with one hand to exercise the wrist muscles. The operation of the wrist exerciser is initiated by providing an effective starting force and/or torque to a rotor inside the hollow casing and thereafter, the rotor can be further rotated with forces applied by wrist muscles. Thus, the initial starting of the rotor is an important issue for operating the wrist exerciser.
The starting of the wrist exerciser is conventionally initiated by forcibly pulling a pull rope that is wound around a circumferential groove defined in the rotor. Examples are shown in the above mentioned Taiwan and US patents. A drawback of this type of wrist exerciser is that the pull rope may easily get deviated out of the circumferential groove of the rotor, leading to incorrect and imprecise rotation of the rotor and thus failure starting of the wrist exerciser. Even when the rotor is correctly started, the rotor can gain no large starting force and initial speed.
U.S. Pat. No. 6,186,914 and Taiwan Patent No. 364383 teach a rack-and-gearing based starting mechanism for starting a wrist exerciser. Sufficient initial starting force and rotational speed can be gained by forcibly pulling the rack with respect to the rotor. However, it is difficult to mate the rack with the gearing after each time the rotor is stopped for the rotor does not always stop at a fixed angular position. A user has to adjust the relative relationship between parts of the wrist exerciser in order to allow engagement of the rack and the gearing. This is certainly troublesome. Further, the rack must be forcibly driven in order to ensure sufficient torque acting upon the rotor. This is not only difficult for certain users but may also hurt the user for the rack that is forcibly pulled may easily contact the hand of the user that holds the wrist exerciser.
US Design D464,687 discloses an electric starter that has a friction roller, which is engageable with rotor of the wrist exerciser for applying a driving force thereto. An obvious drawback is that ready engagement between the friction roller and the rotor is not easily ensured, which makes the operation difficult for certain users. In addition, the friction roller is electrically driven and, once getting in contact with a user's hand that holds the wrist exerciser, may hurt the user's hand. Further, the rotor is not maintained in a specific orbit, and this limits the driving force applied by the friction engagement to the rotor. Thus, similarly, the electric starter cannot ensure a large starting force.
Further, all the conventional wrist exerciser and/or the starting mechanism thereof are operated with two hands and are not suitable for handicapped persons that have one hand available. In addition, the precise engagement required between the conventional starting mechanism and the rotor of the wrist exerciser makes it difficult for the blind to operate the conventional wrist exercisers.
Therefore, it is desired to provide a wrist exerciser that is provided with an auxiliary starting force for efficiently and easily starting the operation of the wrist exerciser with either both hands or a single hand so as to overcome the drawbacks of the conventional devices.